I have a design build that is 240 3 phase at 600 hz, It is powered by a 2 cylinder diesel, driven from the rear crank/pulley.
It is by design a battery charger
But it operates as a power supply to an inverter
, at 12/24/36/48 volts in, and 120/240 out @ 600/60 cycle.
I can charge a large battery
bank 60 feet round trip at 320 amps, 12 v nominal on 3 X #6 cables
, with less then 2% voltage drop, at about 85% machine efficiency. Or power a 5.5KVA inverter.
If you want 60 cycle, I can do that with a hz converter, but if you already have a resilient inverter then that is your hz converter, including a variable speed prime mover.